DynamicModule[{i, pos10 = {{}, {}}, pos11 = {{0, 0, 0}, {0, 0, 0}},
  pos12 = {{0, 0, 0}, {0, 0, 0}}, pos20,
  pos21 = {{0, 0, 0}, {0, 0, 0}}, pos22 = {{0, 0, 0}, {0, 0, 0}}},
 Graphics3D[{

   For[i = 1, i <= 2, i++,
    Print[i];
    EventHandler[
     Dynamic[{Translate[Cuboid[], pos11][[i]]},
      ImageSize ->
       Tiny], {"MouseDown" :> {(pos10[[i]] =
          Mean@MousePosition["Graphics3DBoxIntercepts"])},
      "MouseDragged" :> (pos11[[i]] =
         pos12[[i]] + Mean@MousePosition["Graphics3DBoxIntercepts"] -
          pos10[[i]]), "MouseUp" :> (pos12 = pos11)}];
    ]},
  PlotRange -> {{-3, 3}, {-3, 3}, {-3, 3}}]]